Phenolic resin obtained by polycondensation of formaldehyde, phenol and lignin

Abstract

A lignin-phenol-formaldehyde resin, which is obtained by polycondensation of formaldehyde, phenol and lignin in the presence of a basic or acidic catalyst, is characterized in that the lignin is a lignin that is not chemically modified at the available functional groups. This lignin has a low molecular mass and includes available functional groups chosen from the group including aliphatic hydroxyls and phenolic hydroxyls. The degree of substitution by weight of phenol with the lignin is between 50% and 60%. The weight proportion of the lignin and of phenol in the resin is equal to the weight proportion of phenol in a lignin-free phenol-formaldehyde (PF) resin.

The invention claimed is: 
     
       1. A thermosetting synthetic resin, known as a lignin-phenol-formaldehyde resin, or LPF resin, which is obtained by polycondensation of formaldehyde, phenol and lignin in the presence of a basic or acidic catalyst, wherein the lignin is a lignin that is not chemically modified at the available functional groups, and said available functional groups comprising aliphatic hydroxyls and phenolic hydroxyls. 
     
     
       2. The resin according to  claim 1 , wherein the lignin has a low molecular mass whose Mw is between 700 g/mol and 2000 g/mol. 
     
     
       3. The resin according to  claim 1 , wherein the aliphatic hydroxyls are present in a proportion of from 1.5 mmol/g to 3.0 mmol/g. 
     
     
       4. The resin according to  claim 1 , wherein the phenolic hydroxyls are present in a proportion of from 1.1 mmol/g to 2.0 mmol/g. 
     
     
       5. The resin according to  claim 1 , wherein the resin comprises a degree of substitution by weight of phenol with the lignin which is between 50 and 70%. 
     
     
       6. The resin according to  claim 5 , wherein the resin is synthesised with a formaldehyde to (phenol+lignin) ratio (F/(P+L)) between 35 and 60%. 
     
     
       7. The resin according to  claim 2 , wherein the lignin has a low molecular mass whose Mw is equal to 1500 g/mol. 
     
     
       8. The resin according to  claim 4 , wherein the phenolic hydroxyls are present in a proportion not less than 1.5 mmol/g. 
     
     
       9. The resin according to  claim 5 , wherein the degree of substitution by weight of phenol with the lignin which is between 50% and 60%. 
     
     
       10. The resin according to  claim 6 , wherein the resin is synthesised with a formaldehyde to (phenol+lignin) ratio (F/(P+L)) between 45 and 50%. 
     
     
       11. The resin according to  claim 10 , wherein the resin is synthesised with a formaldehyde to (phenol+lignin) ratio (F/(P+L)) of 47%.